1. Field of the Invention
The present invention relates to a data transmission apparatus, and in particular, to a data transmission apparatus which can transmit a high quality file to a remote site at a high speed.
2. Description of the Related Art
Conventionally, a file transmission has been performed using a TCP/IP protocol. The TCP/IP protocol has a function of re-transmitting data corresponding to erroneous data in the case where an error is generated during transmission, and has features capable of finally performing a file transmission without an error. However, in a line having a transmission path delay, in the case where the above TCP/IP protocol is used, an answer whether or not a data is correctly transmitted from a communication partner is late in coming back; for this reason, at a sender side, a timing of transmitting a new data becomes late. As a result, a problem has arisen such that a through put is reduced. In view of the above problem, a proposal has been made such that a file is divided into multiple portions and they are transmitted by plurality of TCP/IP connections, and thereby, the whole through put is improved.
In a transmission system using the aforesaid plurality of TCP/IP connections, a transmission object file is already existing, and therefore, a premise has been made such that a file size has no change. For this reason,to give an example, in the case of encoding and transmitting an image of two hours, first, a file must be created; for this reason, a problem has arisen such that a user must wait for two hours until a transmission is started. Moreover, in the above transmission system, it is impossible to vary the number of TCP/IP connections. For example, in the case of reduce the number of connections because a network is congested, there is a problem of incapable of reducing the number of connections.
An object of the present invention is to provide a data transmission apparatus which can transmit a high quality file at a high speed. Moreover,another object of the present invention is to provide a data transmission apparatus which can increase and decrease the number of TCP/IP connections in accordance with a situation of network.
In order to achieve the above objects, the present invention has a first characteristics in a data transmission apparatus which performs a data transmission using a plurality of connections, comprising, a data pack creating section for reading a data from a file at a small unit so as to create a data pack, a transmitting section for allocating a data pack created by the data pack creating section to the plurality of connections, and transmitting the allocated data pack, a transmission control section including a transmission control table for controlling a transmitting data, and a retry queue for writing a data pack which has not been transmitted by a failure generated in a certain connection, wherein the transmission section regards a data pack as a transmission object in the case where the data pack exists in the retry queue, and requests a new data pack to the data pack creating section in the case where no data pack exists in the retry queue.
The present invention has a second characteristics in a re-transmission pointer control section which holds a position of a data of a position nearest to the header of the file for data stored in the transmission control table, as a re-transmission pointer.
Furthermore, the present invention has a third characteristics in transmitting/receiving control means for adding a transmitting section and a receiving section during file transmission, and creating a connection between the transmission section and the receiving section, wherein the added transmitting section acquires a data pack from the retry queue or the data pack creating section, and starts transmission in the same manner as the already provided transmitting section.
According to the above first features, a data of the file is read out at a small unit so as to create a data pack, and then, the data pack thus created is allocated to the plurality of connections to be concurrently transmitted. In the case where the data pack is not sent because a failure is generated in a certain connection, the data pack is written into a retry queue, and then, is re-transmitted via a normal connection. As a result, it is possible to transmit a high quality file at a high speed. Further, according to the above second features, in the case where transmission is interrupted, the transmission is restarted from a position held by a re-transmission pointer, and thereby, it is possible to prevent a re-transmission of data already sent, and thus, to improve a transmission efficiency. Furthermore, according to the above third features, it is possible to increase and decrease the number of connections in accordance with a congested situation of transmission path.